What a pro! Britney Spears smiles through the pain of an apparent psoriasis breakout on her ankle

But the pressure on Britney Spears as a judge in the latter stages of Simon Cowell's X Factor seems to be causing the 31-year-old stress that belies her beatific countenance.

The Lucky star is believed to suffer from psoriasis, according to the National Enquirer.

Polished: Britney Spears looked radiant in her leather minidress at The X Factor viewing party held at Mixology 101 at The Grove in Hollywood on Thursday night

Ouch: Poor Britney's ankle looked very sore as braved the red carpet in the highest of heels

And she stepped out at the X Factor
premiere party in Los Angeles on Thursday night looking polished and put
together in a form-fitting leather dress with flower detail.

But red patches on her left ankle and right heel were impossible to miss.

A source told the National Enquirer after a break-out at the beginning of her tenure on the talent show in September:
'Britney has had the skin condition for a long time, but it only flares
up when she's under extreme pressure.

'Now she can't seem to stop
scratching and picking at the sores. She has a psoraisis skin cream, but
she says it burns, so she stopped using it.'

Ouch: Just occasionally Britney winced a little as she stood on the carpet in her high shoes

Flawless: Britney looked radiant and struggled through her appearance with the painful ankle

The causes of psoriasis are not fully
understood but genetics play a strong role. It can appear on any part
of the body and is often itchy.

The condition occurs when skin cells grow at an excelled rate due to the immune system sending out faulty signals.

It appears on the skin’s surface as
red and white scaly patches, although some patients show no
dermatological signs and it is not contagious.

And Britney isn't the only star said to suffer from the autoimmune disease.

Support: Britney was flanked by her fiance Jason Trawick at the ritzy event

Sharing a giggle: Britney smiles with Simon

Kim Kardashian last year revealled to
millions of viewers on Keeping Up With The Kardashians she had developed
the skin disease, exposing an angry red rash that spread from her legs
to her stomach and all over her body.

The reality star is advised in the
episode to lead a slower-paced lifestyle to manage the condition, which
she tapers with make-up.

LeAnn Rimes also hid the disease for
years, and in 2008 finally spoke out in a PSA for the National Psoriasis
Foundation to raise awareness about the condition.

Moment of truth: Britney lost Diamond White (right) but held on to Carly Rose Soneclar (left) is in the last four

On her feet: Britney spent most of the night doing her X Factor judge-ly duty

She told Shape magazine at the time:
'I hid it my whole life. I pretty much got it under control by finding
the right dermatologist and right treatment...

'By finally getting control over it
instead of it having control over me, I wanted to speak out and let
people know that there is hope.

'There are 7million Americans living
with psoriasis and a lot of them are not getting treatment because they
think it's just a rash, when it's really a chronic skin disease that's
been linked to medical conditions like diabetes, cardiovascular disease,
obesity and depression.'

Rimes' campaign was called 'Stop hiding and start living with psoriasis'.